Circuit controlling device



1954 c. R. TURNER ET AL 2,691,082

CIRCUIT CONTROLLING DEVICE Original Filed Oct. 2, 1947 300 CONTACTS I OPEN o C.ONTACTS z 250 CLOSE w 5 LU 200 2 m or I50 E w m z o 5 I 0 5. l0 I 3o 4o SECONDS lrwenifi' //4 .5.

/05 figj *1/04 M Patented Oct. 5, 1954 UNHTED 5TATES ATENT OFFICE 2,691,082 c nema CONTROLLING DEVICE Charles Roger Turner and Paul Garfield Turner, 'Enfield, Springfield Township, Montgomery County, Pa., assignors to Proctor :Electric Company, Philadelphia, Pa., a corporation of llennsylvania 6 claims. 1

This application is a division of application No. 77 7,496,f1led October 2,, l94=7,nowU. S Patent No. 2,641,680, granted June 6, 1953.

The'present invention relates tocontrolof electric circuits and more particularly to a device which is adapted to effect cyclic opening and closing of an electric circuit. While itis intended that the device shall be applicable to any use for which it is suitable, it is especially intended to serve as a wattage controller and/or as a timer.

In some instancesit is advantageous to supply a predetermined aver-age wattage to an electrical load by cyclic opening and closing of the energizing circuit for the load through operation of a thermal wattage controller which comprises a current-operable thermostatic switch. By way of example, such ;a wattage controller may be employed in automatic control apparatus for a pressure cooker, as disclosed in the above-mentioned parent-application. When thus used, the wattage controllerserves to eliect reduced wattage input to a heater, so as to effect reduced heat input to the pressure cooker, after an initial heating up period during which full wattage is supplied to the heater. The same device may also serve to effect intermittent energization of a solenoid-ratchet device to time a pressure cooking operation, as also disclosedi-n the aforementioned parent application.

One object of the present invention is to provide an improved device of the above-mentioned character which is especially well suited to serve as a wattage controller and/or as a timer.

Another object of this inventionis to provide such a device having provision for adjustment of its cycle time, and also having provision for adjustment of the on and off portions of its operatm cycl Other objects and;features of the invention will be apparent from the following description.

In the accompanying drawing,

Fig. 1 is a faceview of a device embodying the present invention;

Fig. 2 is -;a side elevational-view of the device with .the support portion in partial section;

Fig. 3 is a fragmentary view showing the parts in the positions they assume when the switch contacts are open;

Fig. 4 is an explanatory graph; and

Fig. 5 is ,a diagrammatic illustration of the electrical circuit.

Referring first to Figs. 1 to 3, ,the elements of be-dsvic ma ibam untedona commonsup 3. A :billfifihllimmember M33 is activated by a small, electrical heater ,1 Hi4whichpreferably-com- (on. ace-122) prises suitable resistance wire wound about the bimetallic element and insulated therefrom. At its free end, the bimetallic element carries a set screw I 95 which engages a resilient finger I06. A second resilient finger Hi7, which is struck out from the finger Hi6, carries a contact M8 which cooperates with a contact I09 on a stationary rigid arm M il. An over-center spring ,I-H has its ends secured to fingers I06 and it! and forms therewith a toggle-like arrangement. A rigid arm l l2 carries a set screw 55.3 which extends freely through finger I06 for engagement by finger Jill. The bimetal element 5.03 has an opening therein to permit adjustment of screw H3 and to enable movement of the bimetal element without engaging said screw.

In operation, the bimetal element H33 flexes toward the right, as viewed in .Fig. 2, in response to the heating effect of the heater Hi4. As the resilient finger 66 is thus moved toward the right, it passes finger it? and as it does so, the spring ill effects abrupt movement of contact Hi3 out of engagement withcontact I09 and against screw 13. The opening of the contacts interrupts the current flow through the heater EM, and as the bimetal element I93 cools, it moves in the opposite direction until a reverse toggle-like action takes place causin closure of theswitchcontacts.

In Fig. 5, the device is diagrammatically represented in circuit with an electrical load in the form of a heating unit I M. The device operates cyclically to provide a predetermined average wattage input to the heating unit. As hereinbefore mentioned, the device may also serve as a timer. For that purpose a solenoid may be included serially in the circuit of ,Fig. 5 for intermittent energization by the controlling device, and the solenoid may be arranged to actuate a ratchet toefiect a timing action, as disclosed in the aforementioned parent application.

Referringagain to .Figs. 1 to 3, the adjustable set screws Hi5 and ,HS enable .accurate adjustmentof the device both to adjust the average wattage input to a controlled load and to adjust thecycling rate by adjusting the length of the cycle period, the latter adjustment being useful where the device serves as a timer. Adjustment of the set screw M5 varies the temperature which the bimetal element I633 must attain, and therefore the amount of flexing of this element required, to efiect opening of the contacts I08 and Hill by the over-center spring Hi. The adjustment of this screw also affects thetemperature at which the bimetal permits the switch to close xandthus generally may be considered as afiect in; the temperature level at which the device operates. The position of the set screw H3 determines the degree of separation of the contacts 568 and E89 when they are opened by the overceuter sprin l l 2, since the set screw H3 acts as a stop for the resilient contact finger iill. Adjustment or" the set screw iii-i varies the amount of movement of the bimetal element 503, during cooling thereof, which is necessary to cause the over-center spring to close the contacts. The adjustment of screw l thus changes the differential between the temperature at which the binietal m3 opens contacts Hi8 and E69 and the temperature of the biinetal which permits contacts G8 and 1%.: to close.

The two adjusting screws E95 and H3, arrange in the manner described above, greatly Silllp problem of accurately adjusting the device in the factory to give the desired timing action the desired energy input to a control can... It has been found that the number 1 and error adjustments can be minimized by orro'- in the simple procedure of, first, adjusting screw 52-? until the input is correct and, sec- (lllilly, of following this operation by adjustment of the screw M3 to bring the time cycle to its correct value. By performing the adjustments in this order, it is found that the adjusting of screw 3 has little or no effect on the average wattage t. Thus if it were ObEE-"Jfid that the input c too high, turning screw 56:; in the clockwise direc ion. would effect a decrease in the input with a resultant increase in the cycle time. A subsequent adjustment of screw i 53 in the clockwise direction would decrease the cycle time with little an in most cases, no effect on the previously sted input. When the device is used to con t1 01 a pressure cooker, as in the apparatus of the aforementioned parent application, the cycle period of the device is preferably 30 seconds, and and the time of energization of the controlled heating unit during each cycle of the device is preferably 5 seconds.

An additional feature of the device is its ability to compensate for changes of heat output of the .ting element due to changes in line voltage. may be seen with the aid of Fig. 4 which is a g zhic illustration of the operation of the device. In this illustration, the temperature of the bimetal element taken as the ordinate while time is taken as the abcissa. The horizontal dot a d dash line i25 represents the temperature at i h the contacts open, while the dot and dash represents the ten'rperature at which the contacts close. The solid line curve 222 shows the operation. for the normal voltage, i. e. 110 volts. This curve indicates that the on and oil ueriods are 5 seconds and 25 seconds, re-- sp vely. The curve also shows that the tempe ature or the bimetal element overshoots the line before cooling of said element commences. This is due to storage of heat in the heater associated with said element.

Now assume that the voltage rises to 120 volts. This will cause a greater heat output from the heating element i i 6. But the thermal controller com ensates for this by decreasing the on period. As shown in Fig, l, when the voltage increases to 120 volts, the temperature of the bimeta lement rises along the dashed line curve m3 on has a greater slope the rising por on of curve Hence the on time because the t ature or the bimetal *nent rises more o to the open line !29.

over, so tcnperatur 4 and this causes the cooling portion of the n w curve to coincide with the old curve. Therefore the cycle time remains constant.

In the case supposed, the on time is reduced from 5 second to about 4.2 seconds. It can be shown by simple calculation that such reduction of the on time will maintain the heat output of the heating element l M constant, and this has been demonstrated by actual tests.

While a particular form of the invention has been illustrated and described, it will be apparent that the invention is not limited thereto but is capable of various modifications and other embodiments.

We claim:

1. A circuit making and breaking device for effecting accurately timed cyclic opening and closing of an electrical circuit, comprising a switch, electrical heatin means adapted to receive current when said switch is closed, thermomotive means operable by said heating means, means operable by said thermomotive means to open and close said switch upon attainment of different temperatures by said thermomotive means, adjustable means for varying the temperature at which said thermomotive means opens said switch, and other adjustable means for varying the temperature at which said thermomotive means closes said switch, whereby to enable adjustment of the time interval of an operating cycle and also to enable adjustment of the percentage of said time interval during which said switch is closed.

2. A circuit making and brealz'ng device for effecting accurately timed cyclic opening and closing of an electrical circuit, comprising a switch, electrical heatin means adapted to receive current when said switch is closed, means including a ternperature-responsive element for opening and closing said switch upon attainment of different temperatures by said element, adjustable means for varying the temperature at which said element opens said switch, and other adjustable means for varying the temperature at which said element closes said switch, whereby to enable adjustment of the time interval of an operating cycle and also to enable adjustment of the percentage of said time interval during which said switch is closed.

3. A circuit making and breaking device for effecting accurately timed cyclic opening and closlllg of an electrical circuit, comprising a stationary contact, a first resilient arm fixed at one end and carrying a contact engageable with said stationary contact, a second resilient arm fixed at one end and disposed adjacent said first arm, a spring connected between said arms so as to effect snap action of said first arm by movement of said second arm whereby to open and close said contacts, a bimetal arm fixed at one end, heating n cans arranged to heat said bimetal arm and connected in series circuit with said contacts, an adjustable screw on said bimetal arm engageable with said second arm whereby the bimetal arm actuates said second arm, a rigid support member, and an adjustable screw on said support Ill-Ember e geable by said first arm to limit movement of the latter during openin of said contacts.

4. In a circuit making and breaking device for efiecting accurately timed cyclic opening and closing of an electrical circuit, a stationary contact element, a movable contact element cooperatively associated with said stationary element for engagement and disengagement of said elements,

a movable actuating member, an over-center spring connected to said movable contact element and said movable actuating member to move said movable contact element into and out of engagement with said stationary contact element upon movement of said actuating member in opposite directions, a bimetallic member arranged to effect movement of said actuating member in response to heating and cooling of the bimetallic member, an electrical heating element associated with said bimetallic member and connected in circuit with said contact elements, said heating element being energized when said contact elements are engaged and being deenergized when said contact elements are disengaged, whereby said contact elements are cyclically opened and closed, an adjustable screw on said bimetallic member engageable with said actuating member and serving to control the amount of movement of said bimetallic member necessary to effect opening of said contact elements, and a normallystationary adjustable screw engageable by said movable contact element and serving to control the amount of movement of said bimetallic member necessary to effect closing of said contact justing the ratio of the on time to the total cycle time and also adjusting the total cycle time without substantially affecting said ratio, which method comprises first establishing through said first adjustment a particular travel of said thermostatic member on heating to efiect overcenter movement of said spring to cause snap opening of the switch contacts, and then establishing through said second adjustment a particular limit of travel of said switch element on opening of the switch contacts so that a certain movement of said thermostatic member on cooling will efiect oven-center movement of said spring to cause snap closing of the switch contacts.

6. A circuit making and breaking device for eifecting accurately timed cyclic opening and closing of an electrical circuit, comprising switch means including a pair of contacts to open and close said circuit, electrical heating means controlled by said switch means, means including a temperature-responsive element operable by said heating means for actuating said switch means so as to open and close said contacts upon attainment of difierent temperatures by said element, adjustable means for varying the temperature at which said element opens said contacts, and other adjustable means for varying the temperature at which said element closes said contacts, whereby to enable adjustment of the time interval of an operating cycle and also to enable adjustment of the percentage of said time interval during which said contacts are closed.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,521,120 Harrold Sept. 5, 1950 2.521.277 Aubert Sept. 5, 1950 

